/*
  ==============================================================================

   This file is part of the juce_core module of the JUCE library.
   Copyright (c) 2015 - ROLI Ltd.

   Permission to use, copy, modify, and/or distribute this software for any purpose with
   or without fee is hereby granted, provided that the above copyright notice and this
   permission notice appear in all copies.

   THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
   TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN
   NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
   DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
   IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
   CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

   ------------------------------------------------------------------------------

   NOTE! This permissive ISC license applies ONLY to files within the juce_core module!
   All other JUCE modules are covered by a dual GPL/commercial license, so if you are
   using any other modules, be sure to check that you also comply with their license.

   For more details, visit www.juce.com

  ==============================================================================
*/

static const int minNumberOfStringsForGarbageCollection = 300;
static const uint32 garbageCollectionInterval = 30000;


StringPool::StringPool() noexcept  : lastGarbageCollectionTime (0) {}
StringPool::~StringPool() {}

struct StartEndString
{
    StartEndString (String::CharPointerType s, String::CharPointerType e) noexcept : start (s), end (e) {}
    operator String() const   { return String (start, end); }

    String::CharPointerType start, end;
};

static int compareStrings (const String& s1, const String& s2) noexcept     { return s1.compare (s2); }
static int compareStrings (CharPointer_UTF8 s1, const String& s2) noexcept  { return s1.compare (s2.getCharPointer()); }

static int compareStrings (const StartEndString& string1, const String& string2) noexcept
{
    String::CharPointerType s1 (string1.start), s2 (string2.getCharPointer());

    for (;;)
    {
        const int c1 = s1 < string1.end ? (int) s1.getAndAdvance() : 0;
        const int c2 = (int) s2.getAndAdvance();
        const int diff = c1 - c2;

        if (diff != 0)  return diff < 0 ? -1 : 1;
        if (c1 == 0)    break;
    }

    return 0;
}

template <typename NewStringType>
static String addPooledString (Array<String>& strings, const NewStringType& newString)
{
    int start = 0;
    int end = strings.size();

    while (start < end)
    {
        const String& startString = strings.getReference (start);
        const int startComp = compareStrings (newString, startString);

        if (startComp == 0)
            return startString;

        const int halfway = (start + end) / 2;

        if (halfway == start)
        {
            if (startComp > 0)
                ++start;

            break;
        }

        const String& halfwayString = strings.getReference (halfway);
        const int halfwayComp = compareStrings (newString, halfwayString);

        if (halfwayComp == 0)
            return halfwayString;

        if (halfwayComp > 0)
            start = halfway;
        else
            end = halfway;
    }

    strings.insert (start, newString);
    return strings.getReference (start);
}

String StringPool::getPooledString (const char* const newString)
{
    if (newString == nullptr || *newString == 0)
        return String();

    const ScopedLock sl (lock);
    garbageCollectIfNeeded();
    return addPooledString (strings, CharPointer_UTF8 (newString));
}

String StringPool::getPooledString (String::CharPointerType start, String::CharPointerType end)
{
    if (start.isEmpty() || start == end)
        return String();

    const ScopedLock sl (lock);
    garbageCollectIfNeeded();
    return addPooledString (strings, StartEndString (start, end));
}

String StringPool::getPooledString (StringRef newString)
{
    if (newString.isEmpty())
        return String();

    const ScopedLock sl (lock);
    garbageCollectIfNeeded();
    return addPooledString (strings, newString.text);
}

String StringPool::getPooledString (const String& newString)
{
    if (newString.isEmpty())
        return String();

    const ScopedLock sl (lock);
    garbageCollectIfNeeded();
    return addPooledString (strings, newString);
}

void StringPool::garbageCollectIfNeeded()
{
    if (strings.size() > minNumberOfStringsForGarbageCollection
         && Time::getApproximateMillisecondCounter() > lastGarbageCollectionTime + garbageCollectionInterval)
        garbageCollect();
}

void StringPool::garbageCollect()
{
    const ScopedLock sl (lock);

    for (int i = strings.size(); --i >= 0;)
        if (strings.getReference(i).getReferenceCount() == 1)
            strings.remove (i);

    lastGarbageCollectionTime = Time::getApproximateMillisecondCounter();
}

StringPool& StringPool::getGlobalPool() noexcept
{
    static StringPool pool;
    return pool;
}
